1. Field of the Invention
The present invention relates to a melt thermal transfer recording paper. More precisely, the invention relates to a melt thermal transfer recording paper which exhibits good ink transferability and adhesiveness in various printing systems and which, especially when used in a melt thermal transfer recording device, exhibits good hot-melt ink transferability and adhesiveness and good water resistance and solvent resistance.
2. Description of the Related Art
An image recording method includes a sublimation thermal transfer system, a melt thermal transfer system, an electrophotographic system and an electrostatic recording system, and these are widely utilized for recording images and informations. In these, thermal energy is used for transfer and for image fixation and adhesion. For example, an original is pressed against a recording medium via an ink ribbon therebetween so that the colorant is transferred from the ink ribbon to the recording medium, or a toner is transferred onto a recording medium and then adhered thereto by heating it with a high-temperature roll or under light.
Of those, the melt thermal transfer system is generally used for information recording of barcodes and others, and this is driven as follows: A thermal transfer ink ribbon comprising a hot-melt ink and a substrate to support it, and a recording paper are put between a printing head equipped with a thermal head or the like serving as a heat source, and a drum. With that, the thermal head is controlled by an electric signal applied thereto, whereby the hot-melt ink in the thermal transfer ink ribbon is heated and melted, and the resulting ink melt is directly transferred onto the recording paper.
In many cases, the recording paper used in such a melt thermal transfer system has, as its surface, a polyester resin or epoxy resin layer and a primer layer of good adhesiveness to hot-melt ink.
The recording paper of the type is generally a synthetic paper that comprises a stretched film of a propylene-based resin containing an inorganic fine powder such as calcined clay or calcium carbonate (e.g., see JP-A 62-290790, 63-152029, 62-193836, 63-222891, 01-49640, 01-95097, 05-305780, 06-79979, 07-25174, 07-76186, 07-179078, 07-232397, 08-20169, 11-334228, 2000-15941), as well as a stretched polyethylene terephthalate film or a polyolefin-based resin film. Further, the surface of these films is coated with a pigment coating agent that contains an inorganic fine powder such as silica or calcium carbonate and a binder, thereby forming an image-receiving layer thereon so as to increase the whiteness, the colorability and the printability of the films, and these films are used (e.g., see JP-A09-86057, 09-267571, 10-264543, 2000-190433, 2000-218950, 2000-247048, 2001-18542, 2001-225422).
Another type of recording paper is proposed, which comprises a stretched film of an inorganic fine powder-containing polyolefin-based resin and which has an image-receiving layer formed by applying thereto a water-soluble primer of a nitrogen-containing polymer compound for improving the printability and the antistatic property of the film (e.g., JP-A 62-148292). However, when the recording paper is used, then the moisture-absorbing aqueous primer layer absorbs water in high-temperature and high-humidity environments, therefore interfering with the transfer of a hot-melt ink onto it and, as a result, there occur problems in that the lines of the printed barcodes and others may be cut and the printed images may be blurred.
To solve the problems, still another type of recording paper is reported, which is fabricated by applying a water-soluble primer of a nitrogen-containing polymer compound to a stretched porous film of a polyolefin-based resin film that contains an inorganic fine powder of finer particles. It is said that the recording paper may form sharp images thereon even in high-temperature and high-humidity environments (e.g., JP-A 8-80684, 9-76647, 9-295466). However, it is known that, when the printed matter formed by printing on these recording materials is left in high-temperature and high-humidity environments for a long period of time, then there occurs a problem of ink adhesion failure in these.
To further solve the problem, still another technique is reported, which comprises forming a specific image-receiving layer on a recording medium. It is said that, even when the printed matter is left in high-temperature and high-humidity environments for a long period of time, the ink adhesiveness thereto is still good (e.g., JP-A 2001-219661).
However, when barcodes are printed on the recording paper of the type by the use of a melt thermal transfer recording device and when the printed matter is used for information management of drums or containers that contain an organic solvent or the like, then the contents of organic solvent may leak out of them and there occurs a problem in that the hot-melt ink or the image-receiving layer may be dissolved by the organic solvent and the printed information may peel away, and this interferes with the information management. For these reasons, the market much desires the improvement of the recording paper.